The California Air Resources Board issued verifications for diesel particulate filter systems by HUSS Umwelttechnik and by CleanAIR Systems.

The HUSS FS-MK filter has been verified as a Level 3 diesel emission control system, providing an 85% reduction in PM emissions. It can be used with all on- and off-road diesel engines through the 2006 model year, except those equipped with either diesel oxidation catalysts or exhaust gas recirculation systems. The FS-MK series of filters uses a silicon carbide wall-flow filter with a fuel burner for regeneration. The FS-MK system is compliant with the 2009 NO2 emission requirements (≤ 20% increase), and as such has been designated as a “Level 3 Plus” device. (See also the executive order for onroad and off-road verification and the lists of excluded onroad and off-road engine families.)

The ARB has also extended the verification of the CleanAIR Systems Permit™ diesel particulate filter system to include model year 1996-2006 stationary prime and emergency power generators with PM levels of up to 0.2 g/bhp-hr. The filter, a Level 3 device, was previously verified for emergency generators of PM ≤ 0.1 g/bhp-hr.

The Permit™ device is a passively regenerated filter catalyzed with a noble metal catalyst. The filter requires a temperature of above 300°C (about 40% engine load) for at least 30% of operating time or 2 hours, whichever is longer, to regenerate. The filter can be operated for 5000 hours before cleaning/disposal. (See also the executive order, verification letter and engine families.)